The Flip Side

The secrets of conserving the wood behind an early masterpiece.

The Ghent Altarpiece, painted on oak panels, is a touchstone of Western art, and has survived six centuries of tumultuous history.Credit COURTESY SAINT BAVO CATHEDRAL/LUKAS—ART IN FLANDERS

Several of the world’s top experts in the conservation of very old wood covered with very old paint met recently in a windowless, cramped room of the St. Bavo Cathedral in Ghent, Belgium. For two days, they worried over planks that had been cut from Baltic oak trees six centuries ago, probably in Poland, because the Low Countries were already running out of timber. The room, named the Villa Chapel, houses the multi-panelled Ghent Altarpiece, a six-hinged polyptych, measuring twelve feet high by seventeen feet wide when it is fully opened, which is sometimes called “The Adoration of the Lamb,” after its largest panel. The work is believed to have been begun by Hubert van Eyck in the early fourteen-twenties and was finished in 1432, six years after his death, by his brother Jan van Eyck, a revolutionary innovator who was at least as important to Northern European painting as Giotto, a century earlier, had been to Italian painting.

The altarpiece originally inhabited a more elegant but even smaller space in the cathedral, the private chapel of Joost Vijdt, a wealthy textile merchant who had commissioned it. It remained there through six centuries, except for a number of prudent removals—most urgently, to rescue it from Protestant iconoclasts, in 1566, and from a fire, in 1822—and two confiscations, by French soldiers, who filched the central panels in 1794, and by Hitler, who, in 1942, had most of the altarpiece taken from where it had been stored for safekeeping, in France, and hauled first to a castle in Bavaria and then, to avoid Allied bombing, to a salt mine in Austria, where it was discovered by American soldiers in 1945. In 1986, it was relocated to the Villa Chapel, for reasons of security, and enclosed in a huge, aquarium-like box of bulletproof, reflective, greenish safety glass that renders it scarcely seeable and which the restoration experts loathe. Nevertheless, the work is the premier tourist attraction in Ghent, which cannot rival Bruges, Antwerp, or Brussels for their abundance of canonical Flemish art created in the fifteenth and sixteenth centuries under the reigning dukes of Burgundy—notably, Philip the Good, Jan van Eyck’s principal patron, who is otherwise famous for having captured Joan of Arc.

The experts had been charged with assessing the physical condition of the altarpiece, which last underwent a major restoration in 1950-51, and with recommending a site and a design for its future display. Overseen by Anne van Grevenstein-Kruse, from the University of Amsterdam, and the art historian Ron Spronk, from Queen’s University, in Kingston, Ontario, the group included José de la Fuente, from the Prado, in Madrid; Ray Marchant, who works in the Hamilton Kerr Institute’s restoration studio in London; the leading local authority, Jean-Albert Glatigny, from Brussels; and Ingrid Hopfner, from the Kunsthistorisches Museum, in Vienna. They were attended by four “mid-career” conservators from New York, London, Los Angeles, and Budapest, and by three “emerging-level” conservators from Amsterdam, Haarlem, and Brussels, for what amounted to a master class, funded by the Getty Foundation’s Panel Paintings Initiative, in response to an incipient crisis: the majority of the people who are most entrusted with preserving paintings on wood are now in their sixties and seventies, and are soon to retire. The category of their expertise encompasses nearly all early-Renaissance paintings, by artists from Giotto to Fra Angelico—except for frescoes, and for works that were subjected to a once common process that involved gluing paper or fabric to the paint, and, the wood having been chipped away, transferring it to canvas—as well as many Renaissance works, among them the “Mona Lisa.”

New recruits to the field are exhaustively versed in the ethics of conservation and the chemistry and the physics of the materials involved, and they may be adept with X-rays, infrared reflectography, digital macro photography, and other analytic gear. But the intuitive skill that is born of hands-on experience resides chiefly with the aging generation. That group coalesced between the nineteen-fifties and seventies, particularly after the Florence flood of 1966, when sodden masterpieces were fished from the muddy waters of the Arno—a huge wooden crucifix by Cimabue, from 1288, was submerged for two days—and public and private funding brought experts together to share their ideas and apply their talents. Panel restoration was finally standardized, after centuries of miscellaneous and, at times, disastrous practices.

There is no more astounding work of art than the Ghent Altarpiece. Historically, it is a clutch of firsts: it represents the first really ambitious and consummate use of oil paint, though with some admixtures of tempera, and it marks the birth of realism as a guiding principle in European painting. Oils—of linseed, walnut, and other plant extracts—were employed as binders for pigments in Afghanistan in the seventh century and in Europe a century later. Some thirteenth- and fourteenth-century Norwegian altar fronts are all in oils. But nothing that we know of anticipated the eloquence of van Eyck’s glazes, which pool like liquid radiance across his pictures’ smooth surfaces, trapping and releasing graded tones of light and shadow and effulgences of brilliant color.

The effects serve sharply limned figures whose sculptural roundedness, warm flesh, splendid raiment, and distinctive personalities leap to the eye. Anatomical details enthrall: hands that touch and grip with tangible pressures, masses of hair given depth and definition by a few highlighted strands. Over all, the pictures generate a sweet and mighty visual music—which is illustrated in two panels depicting girlish, wingless angels singing and playing instruments. Some scholars have said that the notes they sing are discernible from the shapes of their mouths; an organ is so detailed that a working replica has been made of it. The altarpiece is the sort of art that changes lives. One of the assembled experts, the Belgian art historian and conservator Hélène Dubois, remembered seeing it, as a teen-ager, in the Vijdt Chapel. She said, “The warden opened the wings for us and I was absolutely baffled, fascinated.” She “became obsessed with becoming a conservator of Old Master painting,” she added. “So here I am, in the place I have dreamed about for thirty years.”

There are two ranks of panels, as if of two altarpieces, stacked—a format unique in art history. On the left of the lower tier are views of the horse-riding “Just Judges” and “Knights of Christ”—the former a bland copy, installed in 1945, of the original panel, which was stolen in 1934 and is still missing. (The anti-heroic “judge-penitent” of Albert Camus’s novel “The Fall” possesses that panel, which he contemplates with existentialistically mixed feelings.) To the right are two crowds of hermits and pilgrims, shepherded by St. Christopher. These four panels flank the panorama of the Lamb, which visualizes a verse from Revelations: “After this I beheld . . . a great multitude, which no man could number, of all nations, and kindred, and people, and tongues, stood before the throne, and before the Lamb.” In a wide and deep landscape of grass and trees, with towering cities and blue mountains in the distance, clerics, pagan philosophers, martyrs, saints, and angels approach the Lamb, which stands on an altar. A sparkling fountain trickles water to the bottom of the picture, from where it probably fell to thirsting souls in Purgatory on a predella—a strip of small narrative scenes—that was lost sometime before 1568, when a local writer lamented its ruin by restorers with “calves’ hands.”

The seven pictures on top are surely all Jan van Eyck’s work, except for later retouchings. The central painting is a mystery: Is the youngish, enthroned and bejewelled male figure, holding a crystal sceptre and raising two fingers in blessing, Christ the King or God the Father? Might he somehow be both? The third member of the Trinity appears as a tiny dove in a sunburst over the Lamb. (And isn’t the lamb a symbol of Jesus? The altarpiece still defies thorough interpretation.) The figure is flanked by panels of John the Baptist, who points to him, and the Virgin Mary, who reads a book. (She is beautiful and heart-tuggingly personable: somebody’s daughter, somebody’s sister.) On either side of them are the musical angels. At the far left and right stand Adam and Eve, naked and melancholy, presented like statues in narrow niches but naturalistically vibrant with carnal candor. One of Adam’s feet protrudes, appearing to rest on the frame. When the wings are closed, the Adam and Eve can be swung back open on either side of the central male figure—returned to grace. Painted above them are dramatizations, in grisaille, of Cain’s resentment, and then his murder, of Abel. On the backs of the wings, stonelike figures include an Annunciation: Mary and the angel given slight flushes of color and separated by two panels of the intervening empty room, with a window that overlooks a city. Joost Vijdt, the work’s bald and formidable-looking patron, and his modestly cowled wife, the high-born Elisabeth Borluut, kneel prayerfully in panels of their own. The panels had carved frames, almost all of which have been lost.

On the first day of the examination, the experts, along with junior restorers and students—about two dozen people in all—circulated around the dismounted Mary, John the Baptist, and the “Godfather,” as some of them had taken to calling the ambiguous deity. Other panels had been inspected at an earlier meeting; the major focus this time would be the Lamb. The exquisitely detailed but erratically composed panel, eight feet wide and almost five feet high, displays vestiges of medieval style, as in the clunky clouds which contrast with the meteorologically correct ones on adjoining panels. It also evinces the hands of painters besides Jan van Eyck, who in 1432 employed about a dozen assistants in his workshop. They may include the elusive Hubert, who is not conclusively known to have produced any other painting.

A technician operating big, elaborate cameras was taking hundreds of closeups of the panel, in visible and infrared light spectrums, which will help restorers identify and study the retouchings. The participants came and went through crude plywood-and-steel double doors from the street, temporarily added to a street door for the project. With a few exceptions, including the chic Anne van Grevenstein-Kruse, the group—a guild aristocracy—was unprepossessing, dressed any old way. The white-ponytailed Ray Marchant, who came to the craft from boat-building and cabinetry, was a quiet but palpably formidable presence in the conversations that ebbed and flowed around the room. Ton Wilmering, the project coördinator for the Getty Foundation, spoke of him with awe: “Just picking up a panel in his hands, Ray can exert little pressures and immediately tell you the areas of strength and weakness.” Marchant is a curmudgeonly skeptic of overeagerness in his profession. “Some of the best preserved Old Master paintings,” he wrote to me later, are “those that have been denied ‘improvement’ by restorers.” Accompanying him was his protégée, Britta New, who looked far too young to be a mother of two who lived in a house, outside London, that she had refashioned by hand from a barn. New gave off sparks of fascination while scrutinizing and touching features of the altarpiece’s ancient oak. Tourists were able to view the group, and to see what could be seen of the altarpiece, from a large glass booth, for four euros a person. A junior restorer from Amsterdam, Renzo Meurs, imagined being watched “by the eyes of all art-loving people worldwide.”

On the second day, the Lamb panel reclined, face down, on sawhorses. It struck me as a virtual post-minimalist sculpture: four abutted planks, with numerous wooden cleats of two different sizes glued and screwed across the joins. The smaller cleats were affixed sometime in the nineteenth century. The larger cleats and two heavy iron staples, pounded into the ends of the central join, probably date from 1822, when the panel broke during a panicked removal after the cathedral’s roof caught fire. (The restorers are charged with recommending an emergency procedure for getting the altarpiece out of the building in less than an hour, something that is impossible now, given the constraints of the glass box.) Dings and scratches and traces of an original coating of minium (red lead) on the back of the panel, which was dustily aglow with old wax from the 1950 restoration, looked almost purposeful, like the mechanical “distressing” in faked antique furniture. Contemporary restorers disparage wax, which, a half-century ago, was regarded as a panacea for the ills of old wood. It can be too airtight, for one thing. If the painted front of a panel inhales and exhales any moisture at all, it will swell and shrink by turns, and the wax will prevent the back from moving with it. Eventually, some paint may blister.

Recent flaking has been most rampant on the modern copy of the “Just Judges,” owing to a preparatory sizing of the wood, with glue and resin, that was far inferior to the van Eyck brothers’. The original panels prove to be in fantastically good shape. The restorers checked off one thing after another that needed no correction. No significant cracks have emerged since the last restoration, when the paint surfaces were “consolidated”—their gaps filled in, Anne van Grevenstein-Kruse wrote to me in an e-mail, “with a solution of animal glue (a proteïn). After that, the surface was covered with a mixture of beeswax, colophony, and lavender oil (to soften the paint). This mixture was melted into the paint structure by using strong heating elements. The surface was then flattened with metal spatulas.” Again, wax introduced a problem: “a wax impregnation, being irreversible, precludes to a certain extent other consolidants.”

The planks are of extraordinary quality. They were produced by lengthwise radial cuts to the core of the oak trunks, with the bark and the outer layers of soft sapwood then removed. The tree’s age rings thus evenly stripe the faces of the boards, making them resistant to both warp and flex. The experts’ meeting was preceded by months of tests to measure movement in the wood with the changes in temperature and relative humidity in the room—where hot lights are turned on and off at intervals, and weather intrudes from the street. Though the recorded temperatures swung through thirty-six degrees and the humidity between thirty and eighty per cent, the wood had reacted barely a whisker. When Britta New was asked her opinion of what needed doing, she noted, as if reciting a school lesson, the wrongness of setting cleats against the wood grain. But she immediately acceded to a collective verdict that, absent any sign of ill effect, and given the risks attendant on any intervention, the cleats should stay. Speaking for the instinctive reluctance of responsible restorers, van Grevenstein-Kruse told me that sometimes it is “comforting” to let things be, to “close the door of the bedroom after having covered the child with a warm blanket.”

The distinguished restorer George Bisacca, of the Metropolitan Museum, couldn’t join his peers in Ghent, as he was needed for the installation of the museum’s show of works by the sixteenth-century Flemish painter Jan Gossart. Bisacca is a sturdy, brisk man of fifty-five, the youngest member of panel restoration’s international élite. In the Met’s painting-conservation studios, he briefed me on the arcana of wood. He had trained, in the seventies, at the Workshop of Hard Stones and Laboratories of Restoration, in Florence, the only restoration school in the world where the mastery of woodworking tools is still de rigueur. (The nearest runners-up include the Courtauld and Hamilton Kerr Institutes, in England.) “Other schools have given up,” Wilmering told me, because of the scarcity of qualified teachers on a par with the revered faculty in Florence, and the length and breadth of such training.

Bisacca recalled an exercise: take a four-centimetre cube of wood and plane it down to a three-centimetre cube. I asked his associate Alan Miller, who was one of the mid-level conservators in Ghent, if he had tried that. He said, “Yeah, four or five times.” How close did he come to perfection? “Not very,” he said, wincing. But the effort distinguishes him from academics who are numb to the muscular feel of planes and chisels wielded with hair’s-breadth precision. Wilmering told me, “When you watch George use a chisel, you see him bearing down on the top of it. What you don’t see is the almost equal force, upward, of his other hand.”

I had seen video images of Bisacca and the tall, long-fingered José de la Fuente at work in the Prado on Dürer’s “Adam” and “Eve,” the life-size panels painted in oil in 1507. Dürer used cheap pine for the panels, possibly because he painted them on spec, for later sale. (Most museum-grade Northern European panel paintings are on oak; most Italian panels are on European poplar, a close relative of cottonwood—not the tulipwood that Americans call poplar.) First came the removal, from the back of “Adam,” of a cradle that had been affixed about seventy years ago. Cradles are lattices of glued wooden bars intended to defeat warps and flexes. Usually done by common carpenters, cradling was a standard practice from the middle of the eighteenth century until some years after the Second World War, when curators and conservators began to notice an epidemic of cracks in panel paintings, caused by the wood’s frustrated responses to atmospheric conditions and its own aging. Cradling was regularly performed in combination with a truly miserable tactic: that of thinning—sawing the fronts of panels from their backs. “People were obsessed with keeping the paint film flat,” Bisacca said. “They didn’t see paintings as whole objects, which need to be cared for as such.” Panels painted on both sides were sometimes split, to make two works out of one. Thinning exposes the fragile inner life of ancient boards, which, if they are of a wood other than oak, often harbor damage from chomping and tunnelling insects. (Bugs dislike the tannins in oak.) “It makes the wood much more reactive,” Bisacca said—sometimes to the point of becoming a “cookie,” which you could crumble in your hand.

Six of the eight double-sided panels from the wings of the Ghent Altarpiece were sawn apart in 1894, in Berlin. The panels were in Berlin because, in 1816, after the central panels had been returned to Belgium, following the fall of Napoleon, the Diocese of Ghent sold the wings to a dealer in Brussels, and he, in turn, sold them in Germany, where they ended up in the collection of the King of Prussia. (Today we would call that a deaccession, and screams of protest would fill the air.) They were repatriated more than a century later, as war reparations dictated by the Treaty of Versailles—a loss ominously begrudged by, among other Germans, Hitler. The thinning reduced the panels’ thickness to less than a quarter of an inch. In the nineteen-thirties, they were rejoined with steel frameworks. The paintings appear remarkably little the worse for their ordeal, and the experts in Ghent have opted to recommend letting them be, for now.

At the Prado, with the Dürer resting on its face, Bisacca attacked the cradling on “Adam” with an alarmingly brawny circular saw, adjustable to minutely measured depths, cutting the elements crosswise into hundreds of slices that were then snapped off by hand. It was hair-raising to watch. Then, he and de la Fuente routed out cracks, some of them steeply angled from back to front, almost to the layers of animal glue and gesso that underlie the paint, and filled them in with synthetic resins and adhesives and with wedges and trimmed blocks of centuries-old wood. (Such wood was once readily available in Europe, from orphaned painting stretchers and derelict furniture, but restorers now hoard it.) Finally, the flimsy masterpiece received a device of the Met conservation department’s invention, a wooden support inset with small steel springs and spot-glued to the panel. The springs are tensed to calculated ratios of restraint and forgiveness, sliding from side to side and pushing and pulling in and out, to cope with any future whim of the pine. Paint restorers then repaired the picture, which, before Bisacca and de la Fuente set to work, had suffered more than sixty discrete cracks. Agleam with fresh varnish, “Adam” and “Eve” will be reintroduced to the world at the Prado this week, looking just about brand new.

Bisacca told me about a day, in 2004, when a Duccio popped. He had never experienced anything like it. He was sawing away a mahogany cradle, installed ninety or so years ago, from the back of the small, thick, internally worm-eaten poplar plank that bears Duccio’s “Madonna and Child.” The early-Renaissance painting—it dates from around 1300—is really ur-Renaissance in its epochal leap from medieval taciturnity to humanist pathos: the baby nudges aside his mother’s cowl with one small hand, the better to behold her, and she meets his gaze. The Met had paid a headline-grabbing forty-five to fifty million dollars for the eight-by-eleven-inch item, which works out to more than half a million dollars per square inch of wizened tempera and gold leaf.

Under Bisacca’s hand, a section of the cradle jumped, with a sharp sound that, upon anxious inspection, proved to have been wood language for “Whew!” (Bisacca later imagined having to call the Met’s then director, Philippe de Montebello, with less cheerful news: “Hi. You know that little painting we just got?”) The poplar had been striving to warp, convexly, and was building pressure on the cradle as it did. Eventually—in years or decades—the cradle might have won, rending the panel from top to bottom and crumpling paint adjacent to the split. The Duccio now hangs at ease on velvet under glass at the Met, its subtle curvature no distraction from its dreaming loveliness. Talking with Bisacca has given me new eyes for the physicality of panel paintings. The Met’s show of Jan Gossart (also known as Mabuse) is artistically no great shakes—Gossart brought Italian influences to bear on an Antwerp style that had roots in van Eyck, to an energetic yet decadent effect—but I found myself savoring its sheer quantity of delicate lumber.

One issue concerning the Ghent Altarpiece will be decided by the church wardens of the St. Bavo Cathedral, in consultation with provincial and federal authorities: should the paintings be cleaned? A tiny patch of sky on the Lamb panel had just undergone a test cleaning with mild solvents, including ethanol. It was a far lighter and more resonant blue, of white mixed with ultramarine from lapis lazuli and azurite; the difference was dazzling. But worry dogs the decision. At a meeting of the restorers, a PowerPoint image magnified a zone of lead white that resembled a sun-fissured mud flat, the raised, or “tented,” edges of the cracks having been knocked off by previous cleanings, which, however, had missed ugly brown puddles of decayed varnish. The terrain looked scarily precarious. And, even with highly reliable X-rays, it is not absolutely certain that all of the many retouchings can be distinguished from van Eyck’s brushstrokes: the bathwater might blur the baby. (Today, retouchings are done on a layer of new varnish, so that they can be easily recognized and, if necessary, removed.) That glimpse of sky made me enthusiastic for a cleaning, and I burned with resentment at the bygone meddlers. I told the restorers, “I want to see as much as remains of what van Eyck saw when he finished painting, and nothing that he didn’t.” They all gave me some variant of the same weary look, as if to say, “Oh, to be naïve again.” Dubois later told me that the process would require “extreme concentration, without losing a view of the ensemble.” It is “not for the fainthearted nor the hurried.”

Restorations of much loved works invariably arouse controversy, as in the furor organized against the removal of grime from the Sistine Chapel frescoes between 1980 and 1994. (The result there was sensational, a revelation of Michelangelo’s previously underrated gifts and shoot-the-works gusto as a colorist.) Quite apart from a reasonable wariness of paint loss, sheer loyalty to the wonted look of a work, dirt and all, prejudices many. The experts all tell the story of how, in the thirties, at the Franz Hals Museum, in Haarlem, in the Netherlands, restorers stripped yellowed varnish from some of the paintings. Visitors were so distraught at the change that the museum’s director issued them yellow-tinted glasses. There are also academics who militate against the removal of retouches and even of over-paintings, holding that they embody history in themselves. That’s fine if you dote on archaic hackwork, but maddening if you’d rather view a master’s unadulterated touch.

During the two days of the meeting in Ghent, the Mary, John the Baptist, and “Godfather” panels leaned against a wall in strong light. I got to study them from a nose’s length away. Their sophistication is staggering. The intricacy and sumptuousness of the images are achieved with economical technique. Each of the hundreds of pearls that fringe Mary’s robes is just a dollop of gray hit with a spot of white, so perfectly judged in relative tone that, from any distance, it exudes pearlescence. A seductive softness in the flesh of Mary’s throat owes to one long stroke, indicating a crease, of slightly varied flesh color. Van Eyck understood that realism doesn’t require verisimilitude but only just enough visual cues to exploit the mind’s credulity. We know now, from brain science, that seeing is not a direct register of what meets our eyes but a fast mental construction that squares sensations with memory and desire: what we believe and wish reality to be. Our science would have seemed childishly obvious to van Eyck. His style is synthetic, a repertoire of finesses—some derived from manuscript illumination, which was then the most common mode of painting, and some from the advanced modelling of bodies and drapery found in the sculpture of the time. Van Eyck’s younger contemporary Rogier van der Weyden, in Brussels, improves on it, with a still powerful but more seamless manner; and Hans Memling, later, is smoother yet. But nothing beats the bristling inventiveness of the Ghent Altarpiece. For me, imprinted like many of us with a belief that Renaissance art is a story of Italy, with mere sidelights in other lands, getting to know van Eyck amounts to a crash reëducation. That isn’t easy to get, however, even in Ghent.

By the end of the second day, I felt more confident talking to the restorers than I had when I promoted a cleaning, but my view was even less welcomed when I deplored the four stated options for displaying the altarpiece: where it is now, in the Villa Chapel; where it was originally, in the Vijdt Chapel; in another, somewhat larger, chapel, off the ambulatory of the cathedral’s apse; or in a new chamber to be built in a courtyard of the cathedral complex. The argument for returning it to the Vijdt Chapel, where full-size color photographs of it are installed now, was bolstered by the observation that van Eyck painted all the shadows in the work with the light striking on an angle that aligns with that chapel’s tall window—which, however, has been partially blocked, since 1663, by an obese Baroque altar. Visitors to the smaller room would have to be limited in number, perhaps twenty at a time. “Imagine how special that would be!” van Grevenstein-Kruse said. I wondered, first, about an exhausting wait in line, and then about a ticking time limit for exposure to a work so overwhelming that some minutes of recovery are needed before you can even really start to look at it. The apse chapel suffers from dim light. A custom-made space in the courtyard would enable climate control but not much more square footage.

I envisioned the altarpiece in the center of a vast museum gallery, free of glass and under perfect light. That situation would put into greater play a cultural touchstone that now cannot be truly experienced even by people who visit it more than once. I was given to understand that this will never happen. The prestige and the financial sustenance of St. Bavo and its commercial environs depend on holding van Eyck hostage. The restorers’ final report will appear early next year. It is sure to recommend replacing the grim box with some new configuration of clear, less reflective glass, but to keep the work where it is for now. A general renovation of the cathedral’s interior has begun and is expected to take ten more years to complete. Maybe then the question of where to put the altarpiece can be taken up again. ♦

Peter Schjeldahl has been a staff writer at The New Yorker since 1998 and is the magazine’s art critic.